map rendering

I'm thinking is there a way to render invalidation part only of the whole map when I'm using a pan tool to move the map.

What I mean is when I zoom to a particular zoom of the map. The part of map that I move out of screen will still exist. So next time I move to this part, I do not need to render it again and that will improve the speed.

I think google map is using this tech. I'm using SharpMap 0.9 Mapbox samples